Preprints
Filtering by Subject: Geophysics and Seismology
The rupture extent of low frequency earthquakes near Parkfield, CA
Published: 2018-07-10
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The low frequency earthquakes (LFEs) that constitute tectonic tremor are often inferred to be slow: to have durations of 0.2 to 0.5 s, a factor of 10 to 100 longer than those of typical Mw 1-2 earthquakes. Here we examine LFEs near Parkfield, CA in order to assess several proposed explanations for LFEs long durations. We determine LFE rupture areas and location distributions using a new approach, [...]
Stress change before and after the 2011 M9 Tohoku-oki earthquake
Published: 2018-07-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Megathrust systems hold important clues for our understanding of long- and short-term plate boundary dynamics, and the 2011 M9 Tohoku-oki earthquake provides a data-rich case in point. Here, we show that the F-net moment tensor catalog indicates systematic changes in crustal stress in the years leading up to the M9, due to the co-seismic effect, and for the last few years due to [...]
Coseismic extension recorded within the damage zone of the Vado di Ferruccio Thrust Fault, Central Apennines, Italy
Published: 2018-07-02
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Recent high resolution hypocentral localisation along active fault systems in the Central Apennines illuminates the activation of seismogenic volumes dipping at low angle (<30°) in extensional settings overprinting contractional deformations affecting the continental crust of the Adria microplate. Individuation of the geological structures and of the fault processes associated with these [...]
The slow slip of viscous faults
Published: 2018-06-29
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We examine a simple mechanism for the spatio-temporal evolution of transient, slow slip. We consider the problem of slip on a fault that lies within an elastic continuum and whose strength is proportional to sliding rate. This rate dependence may correspond to a viscously deforming shear zone or the linearization of a non-linear, rate-dependent fault strength. We examine the response of such a [...]
Post-critical SsPmp and Its Applications to Virtual Deep Seismic Sounding (VDSS): 1. Sensitivity to Lithospheric 1D and 2D structure
Published: 2018-06-16
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Virtual Deep Seismic Sounding (VDSS) has recently emerged as a novel method to image the Moho and potentially other lithospheric boundaries. The behavior of SsPmp, the post-critical reflection phase at the Moho that is utilized in VDSS, is rich with complexities not yet widely utilized. Here, motivated by observations from the Ordos Plateau in North China, we use synthetic seismograms computed [...]
Introduction to Interferometry of Fiber Optic Strain Measurements
Published: 2018-06-15
Subjects: Applied Mathematics, Earth Sciences, Geophysics and Seismology, Other Applied Mathematics, Physical Sciences and Mathematics
Distributed acoustic sensing (DAS) measures the average axial strain (strain rate) along a subset of a fiber optic cable, as opposed to the particle displacement (velocity) at a particular small point sensor. In shifting from measuring a vector field to a tensor field, DAS changes the directional sensitivity of measurements of every type of seismic wave when compared to single component [...]
A tutorial introduction to the Hamiltonian Monte Carlo solution of weakly nonlinear inverse problems
Published: 2018-06-11
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present an introduction to Hamiltonian Monte Carlo (HMC) sampling of high-dimensional model spaces with focus on linear and weakly nonlinear inverse problems. This includes the theoretical foundations, intuitive examples, as well as applications to linear and nonlinear, adjoint-based traveltime tomography. HMC rests on the construction of an artificial Hamiltonian system where a model is [...]
New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off
Published: 2018-06-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Stress-dependent nonlinear upper mantle rheology has a firm base in rock mechanical tests, where this nonlinearity results from dislocation creep of minerals. In the last few decades there has been some attention to nonlinear, power-law, materials for application in scaled analogue experiments for tectonic processes. However, studies describing the rheology of analogue materials with the same [...]
Off-fault Focal Mechanisms not Representative of Interseismic Fault Loading Suggest Deep Creep on the Northern San Jacinto Fault
Published: 2018-06-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Within the San Bernardino basin, some focal mechanisms show normal slip that is inconsistent with the expected interseismic strike-slip loading of the region. The discrepancy may owe to deep (> 10 km depth), creep along the nearby northern San Jacinto fault. The enigmatic normal slip microseismicity occurs to the northeast of the fault and primarily below 10 km depth, consistent with off-fault [...]
Coulomb pre-stress and fault bends: ignored yet vital factors for earthquake triggering
Published: 2018-06-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Successive locations of individual large earthquakes (Mw>5.5) over years to centuries can be difficult to explain with simple Coulomb stress transfer (CST), because seismicity can miss out nearest-neighbour along-strike faults where coseismic CST increases are greatest. We show that “Coulomb pre-stress” may explain this, because magnitudes are >±50 bars if interseismic loading and local [...]
The impact of earthquake cycle variability on neotectonic and paleoseismic slip rate estimates
Published: 2018-05-29
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Because of the natural variability (aleatoric uncertainty) in earthquake recurrence intervals and coseismic displacements on a fault, cumulative slip on a fault does not increase linearly or perfectly step-wise with time; instead, some amount of variability in shorter-term slip rates results. Though this variability could greatly affect the accuracy of neotectonic (i.e., late Quaternary) and [...]
Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation
Published: 2018-05-28
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics, Volcanology
Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid‐filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a [...]
Crack models of repeating earthquakes predict observed moment-recurrence scaling
Published: 2018-05-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Small repeating earthquakes are thought to represent rupture of isolated asperities loaded by surrounding creep. The observed scaling between recurrence interval and seismic moment, Tr ~ M^(1/6), contrasts with expectation assuming constant stress drop and no aseismic slip (Tr ~ M^(1/3)). Here we demonstrate that simple crack models of velocity-weakening asperities embedded in a [...]
Time scales of shallow magma chamber replenishment at Campi Flegrei caldera.
Published: 2018-05-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Ascent of primitive magmas from depth into shallow, partially degassed reservoirs is commonly assumed to be a viable eruption trigger. The resulting processes of convection and mixing have played an important role both in pre- and syn-eruptive stages in many eruptions of different sizes at the unrest Campi Flegrei caldera in Southern Italy. We performed numerical simulations of magma chamber [...]
Measuring Higher-Mode SurfaceWave Dispersion Using a Transdismensional Bayesian Approach
Published: 2018-05-22
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a method for measuring the dispersion of higher mode surface wave phase velocities from a single seismogram using a hierarchical transdimensional Bayesian approach. The 1-D shear velocity profiles down to 800km depth between sources and seismic stations are regarded as the controlling parameters to tune the phase velocities of fundamental and higher modes. The misfits between [...]